[1] UCL, Div Psychol & Language Sci, London WC1E 6BT, England
[2] Univ Laval, Quebec City, PQ G1K 7P4, Canada
[3] Univ Montreal, Int Lab Child & Adolescent Mental Hlth Dev, Montreal, PQ H3C 3J7, Canada
[4] Kings Coll London, Inst Psychiat, MRC Social, Genet & Dev Psychiat Ctr, London, England
[5] INSERM, U669, F-75654 Paris 13, France